I've been married twenty years. It's actually kinda simple.
1. She don't like the stuff you like to do. So, she is never going to be interested in any cost involved with any of those hobbies.
2. She don't like the mess that your stuff leaves around the place. Which goes back to point #1.
3. It's always easier to get forgiveness than it is to get permission.
If you drag this out and turn it into a fight, it will just kill and enjoyment and will turn your hobby into an issue. If you continue to do what you are doing now, it is simply going to turn your hobbie and the clutter into an issue. If you just build what you need when she aint home, and put all your stuff neatly away and get it out of her areas, you will see that "wow, it looks so much better" and bitch a little bit about the money you spent. A week from now, you will be doing what you want to be doing and she will have forgotten all about the "extra money" your hobby costed and be happy that the yard looks so much better. Plus, if you every happen to get good enough to make some stuff you can sell, she'll be even happier with the money.
It comes down to this. Your hobby, your house, the money and the areas belong to both of you. You can't take ownership of an area. And, "ONE" of you can't always be in control. Share and share alike. If she knits or something like that, don't bitch about her stuff either. Compromise. Either way, if you just do it ....... she'll forget about it long before we see one of your knew projects made in your new space posted on here ..... LOL.
The risk is up to you.
Mutt